Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.34	3.412%	$213.3803	$213.38	$213.40	$213.40
Purchase #2	$160.47	8.103%	$173.4729	$173.47	$173.45	$173.50
Purchase #3	$127.34	13.487%	$144.5143	$144.51	$144.50	$144.50
Purchase #4	$68.49	8.110%	$74.0445	$74.04	$74.05	$74.00
Purchase #5	$57.84	12.841%	$65.2672	$65.27	$65.25	$65.30
Purchase #6	$10.98	5.761%	$11.6126	$11.61	$11.60	$11.60
Purchase #7	$243.93	7.658%	$262.6102	$262.61	$262.60	$262.60
7 purchase totals =	$875.39		$944.9020	$944.89	$944.85	$944.90